Reference is made to commonly assigned U.S. patent application Ser. No. 09/012,842 filed Jan. 23, 1998, entitled xe2x80x9cAddressing Non-Emissive Color Display Devicexe2x80x9d to Wen et al; U.S. patent application Ser. No. 09/035,516 filed Mar. 5, 1998, entitled xe2x80x9cHeat Assisted Image Formation in Receivers Having Field-Driven Particlesxe2x80x9d to Wen et al; U.S. patent application Ser. No. 09/034,066 filed Mar. 3, 1998, entitled xe2x80x9cPrinting Continuous Tone Images on Receivers Having Field-Driven Particlesxe2x80x9d to Wen et al; U.S. patent application Ser. No. 09/037,229 filed Mar. 10, 1998, entitled xe2x80x9cCalibrating Pixels in a Non-emissive Display Devicexe2x80x9d to MacLean et al; U.S. patent application Ser. No. 09/054,092 filed Apr. 2, 1998, entitled xe2x80x9cColor Image Formation In Receivers Having Field-Driven Particlesxe2x80x9d to Wen et al; U.S. patent application Ser. No. 09/075,081 filed May 8, 1998, entitled xe2x80x9cColor Image Device With Integral Heatersxe2x80x9d to MacLean et al. The disclosure of these related application is incorporated herein by reference.
This invention relates to an image-forming device having field-driven particles.
There are several types of field-driven particles in the field of non-emissive displays. One class uses the so-called electrophoretic particle that is based on the principle of movement of charged colloidal particles in an electric field. In an electrophoretic image-forming device, the charged particles containing different reflective optical densities can be moved by an electric field to or away from the viewing side of the device, which produces a contrast in the optical density. Another class of field-driven particles are particles carrying an electric dipole. Each pole of the particle is associated with a different optical densities (bi-chromatic). The electric dipole can be aligned by a pair of electrodes in two directions, which orient each of the two polar surfaces to the viewing direction. The different optical densities on the two halves of the particles thus produces a contrast in the optical densities.
Electrophoretic image-forming devices are limited to reflective applications. It is desired to produce a transparent electrophoretic image-forming device for transmissive applications.
Electrophoretic image-forming devices are also limited in their ability to produce high contrast and sufficient color gamut. It is desired to produce an electrophoretic image-forming device with improved contrast and color gamut.
To produce a high quality image, it is essential to form a plurality of image pixels by varying the electric field on a pixel wise basis. The electric fields can be produced by a plurality pairs of electrodes embodied in the display as disclosed in U.S. Pat. No. 3,612,758. One difficulty is in displaying color images. The field-driven particles of different colors need to be provided in discrete color pixels. This approach requires the colored particles to be placed in precise registration corresponding to the electrodes. This approach is therefore complex and expensive.
An additional problem in the displays comprising field-driven particles is forming images that are stable. Typically the images on these displays must be periodically refreshed to keep the image from degrading.
It is an object of the present invention to provide an improved way of providing field-driven electrophoretic suspensions which can readily form images in displays and receivers.
It is a further object of the present invention to provide an electrophoretic image with improved contrast and color gamut.
These objects are achieved by a display which uses a suspension fluid for producing pixels of an image, comprising:
a) at least one image-forming layer having a structure which defines a plurality of pixels, the structure including means for receiving a suspension fluid having light absorbing field-driven particles where, in a first condition, the field-driven particles present a reduced surface area to absorb a reduced portion of incident light and, in a second condition, present a wider surface area to absorb an increased portion of incident light;
b) at least one electric field forming means for selectively applying electric fields to the image-forming layer which acts upon at least one pixel and its field-driven particles in the suspension fluid; and
c) electronic control means coupled to the electric field forming means so that electric fields are selectively applied at locations on the image-forming layer corresponding to pixels in response to a stored image thereby effecting changes in the position of the field-driven particles to cause the production of an image in the image-forming layer corresponding to a stored image.
These objects are also achieved by a transparent image producing receiver which uses a suspension fluid for producing pixels of an image, comprising: at least one image-forming layer having a structure which defines a plurality of pixels, with the structure including means for receiving a suspension fluid having field-driven particles, which move in response to an externally applied field, where, in a first condition, the field-driven particles produce a first level of transmitted incident light and, in an second condition, produce a second level of transmitted incident light.
An advantage of the present invention is that a transparent electrophoretic image-forming display and receiver are provided for use in transmissive applications.
A further advantage is that a multiple layer color electrophoretic imaging displays and receivers are provided resulting in improved contrast and color gamut.